In Googling "drill bit guide" came across this and other tools like it:

Something like this seems perfect for being able to drill a straight hole through wood. However, I can't seem to find anything like it at Lowe's, Home Depot, or Menard's. Surely, I must not be searching properly as it would appear that such a tool would be a very handy addition to one's arsenal of precision tools.

What, exactly, is the industry term for such a tool that makes for the easy centering of a drill bit?

I'm afraid the only proper solution is a drill press. Anything else is a poor approximation. Obviously not a practical solution for most of us. Most of us do the best we can to come close. Hope what ever you do works out for you.
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bcworkzDec 30 '12 at 22:38

Are you pilot drilling first? Whether or not you use a guide, a drill press, or freehand, pilot drilling will result in more precise starting position and path of the hole. Even CNC machines are usually programmed to pilot drill holes beyond a certain depth and usually center drill all holes before running the final bit through.
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alx9rDec 31 '12 at 20:59

6 Answers
6

I am answering my own question here with an awesome, home-grown solution to my problem. I fastened two pieces of wood together at a 90 degree angle. Corner clamps made it easy to get it perfect. I then took a third piece of wood and cut a 45 degree bevel off the corner. This piece is my drill bit adapter that fits a number of larger-sized drill bits, but was made with my 3/8" bit in mind. I also made another for smaller sizes (not shown).

To hold the adapter firmly in place and tight against the bit, I use one of my smaller c-clamps. Using this custom guide, I was able to drill a near-perfect hole into the subject. I also used another similar custom assembly that works with a plug cutter bit for my power drill.

In my quest to the perfectly perpendicular and/or perfectly placed hole, I have tried multiple solutions but the truth is, for truly, 100% accuracy you need:
A high-quality drill press with a chuck that is made to tight specifications. Then, you need to calibrate it with a special dial indicator (even drill presses drill inaccurate holes out of the box). Must calibrate the table left-to-right and in many cases the front-to-back needs some work as well. It is the only way to make a hole truly perpendicular to the face of the piece you are working on.

Then, no standard drill bit will work on metal (for wood this is not as critical) without a bit of wandering: they usually deflect a bit and "walk" slightly to one side before penetrating the material. This is more so in hard metal than on soft alloys but it happens almost all the time, even if you start with a smaller bit and enlarge the hole with subsequent passes with larger bits.

To solve this you need a "Center Drill".
This are very short and hard bits made specifically for this purpose. You use them to drill a tine hole, always smaller than the final hole you need but it will give your final-size bit a depression where it will start to drill WITHOUT deflecting.

Now, this level of accuracy is only needed is some situations but the point of this post was to pass some info I have gathered by researching the subject in depth and then my own trial-and-error not to mention a lot of cash spend on tools.
I can say after all this money and time spent I can make a hole in almost any material right where I want it, less than a thousand of an inch off, without breaking any drill bits.

To top it off, you cannot make a perfectly round hole with a drill bit, if you want to take it to the extreme, you need to finish with a drill bit slightly smaller than the true hole size you want and then use a reamer (again, mostly for metal drilling and more pronounced with the larger bits).

I understand this is taking it into the machinist territory but I am not a machinist and enjoy seeing how accurate I can be in my work/hobbies, sometimes well beyond what is needed, just to see how far I can go.

Once when I needed to drill a series of precisely placed holes with a small diameter drill bit (was drilling a printed circuit board) and my small bit was wandering too much, I clamped the bit in a vice and snapped off half of it so it was short enough to let me push it all the way back into the chuck so only about 1/4" stuck out -- that took care of the wandering bit. At the time (well, even today), I'd never heard of a "Center Drill", that probably would have been a superior solution.
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JohnnyJan 28 at 19:18